/* -------------------------------------------------------------------------
 *
 * pg_crc32c_choose.cpp
 *	  Choose which CRC-32C implementation to use, at runtime.
 *
 * Try to the special CRC instructions introduced in Intel SSE 4.2,
 * if available on the platform we're running on, but fall back to the
 * slicing-by-8 implementation otherwise.
 *
 * Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/common/port/pg_crc32c_choose.cpp
 *
 * -------------------------------------------------------------------------
 */

#include "c.h"

#ifdef HAVE__GET_CPUID
#include <cpuid.h>
#endif

#ifdef HAVE__CPUID
#include <intrin.h>
#endif

#include "port/pg_crc32c.h"

#if defined(__aarch64__) && defined(__GNUC__)

#ifdef __cplusplus
extern "C" {
#endif

extern int crc32_arm(const void* buffer, unsigned int length, int seed);

uint32 pg_crc32c_hardware(uint32 crc, const void* data, Size len)
{
    return (uint32)crc32_arm(data, len, crc);
}

#ifdef __cplusplus
}
#endif

#else

static bool pg_crc32c_sse42_available(void)
{
    unsigned int exx[4] = {0, 0, 0, 0};

#if defined(HAVE__GET_CPUID)
    __get_cpuid(1, &exx[0], &exx[1], &exx[2], &exx[3]);
#elif defined(HAVE__CPUID)
    __cpuid(exx, 1);
#else
#error cpuid instruction not available
#endif

    return (exx[2] & (1 << 20)) != 0; /* SSE 4.2 */
}

/*
 * This gets called on the first call. It replaces the function pointer
 * so that subsequent calls are routed directly to the chosen implementation.
 */
static pg_crc32c pg_comp_crc32c_choose(pg_crc32c crc, const void* data, size_t len)
{
    if (pg_crc32c_sse42_available()) {
        pg_comp_crc32c = pg_comp_crc32c_sse42;
    } else {
        pg_comp_crc32c = pg_comp_crc32c_sb8;
    }

    return pg_comp_crc32c(crc, data, len);
}

pg_crc32c (*pg_comp_crc32c)(pg_crc32c crc, const void* data, size_t len) = pg_comp_crc32c_choose;
#endif /*defined(__aarch64__) && defined(__GUNC__)*/
